This year, the American Cancer Society estimates more than 1.4 million cases of cancer will be diagnosed in the U.S. About 565,650 Americans will die of the disease. The most common cancers among men are prostate, lung and colorectal. Among women, the leading cancers are breast, lung and colorectal.

When cancer is suspected, the only way to make a confirmed diagnosis is through a biopsy. A small tissue sample is taken and a pathologist examines it under a microscope, looking for changes or characteristics associated with cancer. A biopsy can help doctors find out what type of cancer is present and determine the stage of the cancer.

Another type of diagnostic procedure, called cytology, examines the individual cells or groups of cells extracted from body fluids. In some cases, the cells may be smeared directly onto a glass slide (called a smear) and sent to the lab for staining and examination under a microscope by a cytologist or pathologist. When large amounts of body fluid are removed, the sample is processed to concentrate and extract the cells. The cells are then stained and examined.

Cancer Cells versus Normal Cells

Under a microscope, there are some characteristic differences that help cytologists or pathologists determine whether the slide contains cancer cells or healthy cells. For example, cancer cells often have an abnormal shape and size. They often have a larger cell nucleus and appear darker after staining. They may also group together or function differently than normal cells from the target area of the body. Jianyu Rao, M.D., a Cytopathologist with UCLA, says in body cavity fluids, however, some cancer cells can look similar to normal cells.

One characteristic that sets cancer cells apart from normal cells is softness, or elasticity of the cell. All cells contain a type of scaffolding, called the cytoskeleton, to help them hold their shape. As a cancer cell matures, its cytoskeleton changes, causing the cell walls to become soft and flexible. Researchers believe this new-found flexibility is what enables the cancer cells to squeeze through small blood vessels and eventually spread through the body.

A New Tool

Rao and his colleagues recently used a special diagnostic tool, called an atomic force microscope (AFM), to compare the softness of cancer cells against normal cells. An AFM contains a tiny, sharp probe and a finely sensitive cantilever that bends under minute pressure. Once a cell sample is prepared on a slide, the tip of the AFM is pushed onto the cell. Normal cell walls are strong and will resist the pressure of the tip, causing the cantilever to bend. Cancer cells, on the other hand, will give with the pressure and cause less bending of the cantilever. Researchers can correlate cell wall stiffness with the degree of bending of the cantilever.

In a recent study, the researchers studied cells of fluid samples from patients with suspected metastatic lung, breast and pancreas cancer. The investigators found cancer cells were about 70 percent softer than healthy cells.

More studies are needed to confirm the accuracy/benefits of atomic force microscopy. The technique isn't widely available and not likely to replace traditional biopsies or cytology testing. However, it may prove to be useful when performed in conjunction with other testing techniques, especially when results are inconclusive or still suspect after a negative result. In the future, AFM may also be useful to test a cancer cell's responsiveness to drugs.

For general information on cancer, diagnosis or treatment:

American Cancer Society

National Cancer Institute